FABRICATION OF CERAMIC HIGH TEMPERATURE MICROSYSTEMS

This paper reports on recent advances in fabricating alumina-based ceramic microcombustors for applications in high temperature microsystems. We have fabricated alumina structures with critical dimensions on the order of 1 mm or less by using a gel-casting approach with poly(vinyl) alcohol (PVA) as a non-toxic polymeric binder. Polymer binder content, alumina weight ratio, and thermal cycling were varied systematically to develop microcombustors that can sustain stable flames in a spiral configuration allowing for better mixing of fuel and oxidizer streams for a more uniform heat output. The polymer binder and cross-linker content varied between 10 and 20 % (w/v to DI water) and 50 and 100 % (w/w to PVA) respectively to obtain an optimal binder content. The weight ratio of alumina (w/w 30-50%) in the binder solution was evaluated with 1.1 micron particles to observe the effect on the green body density. The green body was then fired in a high temperature furnace in air to bum-out the polymeric binder and sinter the ceramic. Heating and cooling rates, maximum operation temperature, and dwell times were evaluated to obtain high density ceramic structures with 50% or higher alumina content. Thermal stress and heating and cooling rates appear to be major parameters to control in order to obtain high-quality microcombustors.